The dome failed at a repair patch that had been improperly welded and did not provide the minimum thickness needed to contain the dome’s operating pressure. The steel mill’s mechanical integrity program lacked effective inspection and weld repair practices, contributing to the incident.
In iron manufacturing, a blast furnace operates at high temperatures to convert iron ore into molten iron. Hot, pressurized air enhances the blast furnace’s efficiency and capacity. This hot air is heated in a pressure vessel known as a stove, and the top hemispherical part of the stove is referred to as the dome. On July 16, 2020, a blast furnace at the Burns Harbor mill, Blast Furnace D (“Blast Furnace”), was operating normally when the dome on one of its stoves suddenly and catastrophically separated at approximately 6:30 a.m., resulting in a large explosion. Plant operators shut the unit down within minutes. The incident severely damaged portions of the mill.